Boosting Alkaline Hydrogen Evolution via Synergistic Reverse Hydrogen Spillover and Metal–Support Interactions in Ni–Ru Alloy Clusters on Nitrogen-Doped Carbon

To enable the large-scale implementation of the hydrogen evolution reaction (HER) in alkaline electrolytes, obtaining highly active and economical electrocatalysts remains a crucial requirement. In this work, ultrafine Ni–Ru alloy nanoclusters and atomically dispersed Ru–N4 and Ni–N4 sites were successfully anchored on nitrogen-doped hollow mesoporous carbon spheres (NHMCS) via a microwave-assisted solvothermal method within 15 min, yielding Ni–Ru bimetallic catalysts (NixRuy/NHMCS). In 1.0 M KOH, the NiRu4/NHMCS-900 catalyst delivered outstanding HER performance, characterized by a record-low overpotential of 9.3 mV at 10 mA cm–2. This value is notably lower than that of the commercial Pt/C catalysts. Moreover, the catalyst demonstrated remarkable stability over 100,000 cycles and sustained performance during 120 h of continuous operation. X-ray absorption fine structure (XAFS), in situ Raman spectroscopy, and density functional theory (DFT) calculations collectively demonstrate that the outstanding HER activity is governed by the synergy of Ni–Ru bimetallic sites and the reverse hydrogen spillover effect (HSE) between the NHMCS and metal clusters. Specifically, nitrogen sites in NHMCS initially adsorb H2O molecules, which then dissociate into N–H intermediates. The resulting adsorbed hydrogen atoms (Had) migrate to adjacent Ru sites, forming Ru–H intermediates that subsequently evolve into H2 gas. Simultaneously, Ni sites interact with hydroxyl groups to form Ni–OH species, modulating the electronic structure and stabilizing key intermediates. Additionally, the porous NHMCS architecture and strong metal–support interactions (MSI) prevent the aggregation of Ni–Ru clusters, further enhancing structural integrity. This study offers new insights into designing high-performance HER catalysts by harnessing reverse hydrogen spillover and bimetallic synergy.